Naturally Kiawah Magazine Volume 40 | Page 12

Figure 4. Kiawah’s northeast end shows the abundant vegetated beach ridges (foreground) and enormous volume of sand provided by the Stono Inlet ebb-tidal delta. Waves breaking in the distance (top of photo) show the extent of the delta’s lobe. (Photo by L. Sautter, 2008). How do these related processes of tidal currents and wave energies shape Kiawah Island? Kiawah is a northeast- southwest trending barrier island of approximately 9.7 miles in length. The island’s outline has a shape that Dr. Miles Hayes likened to a drumstick, with the bulbous “meaty” end (2.5 miles wide) near to Stono Inlet (Figure 3). Much of the sand that comprises this bulbous end was transported by waves from the inlet’s ebb-tidal delta to Kiawah’s beach. Large sand bodies called swash bars periodically detach from the delta and wave energy allows the sand to migrate slowly landward and weld onto the downdrift beach. In some cases, enough sand accretes so that the wind can form dunes that subsequently become vegetated with sea oats and dune grasses. These early plants are highly tolerant of the ocean’s salty spray and help to anchor the dunes, forming vegetated beach ridges (Figure 4). Over long periods of time more swash bars detach from the ebb-tidal delta and weld onto the downdrift beach. New dunes build seaward of old dunes, and less salt-tolerant plant species are then able to take hold in the partially protected 10 environment of the second through fourth (or more) rows of beach ridges. Eventually, the seaward accretion of the shoreline thoroughly protects the oldest vegetated beach ridges from the ocean’s salt spray, allowing live oaks to take hold and thrive. Live oak and Palmetto trees establish what is known as the maritime forest for our region. These two plants are referred to as the climax species that no other vegetation species in this environment can out-compete. Longshore transport toward the southwest distributes some of the ebb-tidal delta sand that was welded onto the shore, providing abundant sand to Kiawah’s downdrift beaches. Transported sand moves down the beach in the zig-zag pattern described above, and eventually reaches a barrier island’s downdrift inlet. Many sand grains enter the inlet and are swept by tidal currents out to the inlet’s ebb-tidal delta. Other grains, though, may be deposited at the island’s terminus, at the edge of the inlet. This accretion allows the island to “grow” in the downdrift direction, creating an elongate feature known as a recurved spit (Figures 3 and 5). The spit is analogous to a drumstick’s handle and often has Naturally Kiawah